const landDom = document.getElementsByClassName('land')[0];
const landStyle = getComputedStyle(landDom);
const landWidth = parseFloat(landStyle.width);
const landHeight = parseFloat(landStyle.height);
const landLeft = parseFloat(landStyle.left);
const landTop = parseFloat(landStyle.top);

class Land extends JuXing {
    constructor() {
        super(landWidth, landHeight, landLeft, landTop, -100, 0, landDom);
    }
    onMove() {
        if (this.left <= -landWidth / 2) {
            this.left = 0;
        }
    }
}